1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a method and a device for coating polyimide.
2. The Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications. Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The principle of operation of the liquid crystal display panel is that with liquid crystal molecules interposed between two parallel glass substrates, electricity is applied to the glass substrates to control the liquid crystal molecules to change direction in order to refract out light emitting from the backlight module for generating images.
Generally, the liquid crystal display panel is composed of a color filter (CF) substrate, a thin-film transistor (TFT) substrate, liquid crystal (LC) interposed between the CF substrate and the TFT substrate, and sealant. The liquid crystal display panel often needs to coat polyimide (PI) on the TFT substrate and the CF substrate and to form a pre-tilt angle by subjecting polyimide to rubbing or photolithography in order to provide the liquid crystal molecules with a carrying angle.
Heretofore, coating of polyimide is achieved with the following way. Polyimide is uniformly applied to a printing plate (Asahikasei Photosensitive Resin (APR) plate) and polyimide is transferred by means of a roller from the printing plate to the TFT substrate or the CF substrate with the TFT substrate or the CF substrate being simultaneously moved in plane to complete the coating of polyimide. However, the known devices for coating polyimide are very complicated and the operation time of coating polyimide is extended so that polyimide may readily flow away from opposite sides of the TFT substrate or the CF substrate, resulting in waste of material.